Under typical operating conditions, lubricants are subject to extremes of cold and hot temperatures. Ashless detergents are necessary for low temperature lubricant operations to prevent the formation of what is known as "cold sludge" which results from water present in the lubricant. During high temperature operation, antioxidant additives are necessary to prevent oxidative degradation of the lubricant. Oxidation of a lubricant can lead to the build-up of oil-soluble acids and lacquers and sludge which cause serious damage to engines and other lubricated systems. Typically, antioxidant additives are blended with lubricants in order to improve the stability of the lubricant and thereby enhance the ability of the oil t resist oxidation.
In formulating lubricants for use in marine environments, such as those used in marine diesel engine and steam turbine applications, special concern is directed to using lubricant additives which will inhibit acid catalyzed oxidation and, at the same time, promote good separation between oil and water. Otherwise, the water which unavoidably finds its way into the lubricant reservoir forms an emulsion and contaminates the lubricant; thus, for example, marine oils should be able to separate from water rather than form stable emulsions. Surface active compounds such as metal surface protectors are prone to impair the demulsifying properties of the oil. Accordingly, there is a need for dispersants with good antiwear and anticorrosion properties while maintaining good water-to-oil separation.